Integrated processing and critical point drying systems for semiconductor and mems devices

ABSTRACT

Processing and drying of a sample, such as a semiconductor or MEMS device, is achieved using a single pressure chamber. The pressure chamber holds the sample in a sealed interior volume throughout various process steps, such as, but not limited to, photoresist removal, sacrificial layer etching, flushing or rinsing, dehydration, and critical point drying. The pressure chamber is constructed of a chemically-resistant and pressure-resistant material to withstand the various chemicals and pressures that are encountered in the various process and drying steps. For example, the pressure chamber is constructed from a nickel-copper alloy. Automated release etching and critical point drying of a MEMS or semiconductor device is provided without removing the device from the sealed pressure chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. application Ser. No.13/695,784, filed Nov. 1, 2012, which is a U.S. national stage ofInternational Application No. PCT/US10/39980, filed Jun. 25, 2010, bothof which are hereby incorporated by reference herein in theirentireties.

FIELD

The present disclosure relates generally to systems for integratedprocessing and drying of samples, and, more particularly to systems forintegrated processing and critical point drying of semiconductor and/ormicroelectromechanical system (MEMS) devices in a single chamber.

SUMMARY

Processing and drying of a sample, such as a semiconductor or MEMSdevice, is achieved using a single pressure chamber. The pressurechamber can hold the sample in a sealed interior volume throughoutvarious process steps, such as, but not limited to, photoresist removal,sacrificial layer etching, flushing or rinsing, dehydration, andcritical point drying. The pressure chamber can be constructed of achemically-resistant and pressure-resistant material to withstand thevarious chemicals and pressures that are encountered in the variousprocessing and drying steps. For example, the pressure chamber may beconstructed from Monel, which is a nickel-copper alloy resistant to manyof the chemicals commonly employed in MEMS and semiconductormanufacturing. Fluid conveyances connected to the pressure chamber mayalso be constructed from the chemically-resistant material.

In embodiments, an apparatus for processing of a sample can include apressure chamber with an interior volume constructed to receive thesample therein. The pressure chamber can have at least one inlet influid communication with the interior volume. The apparatus can alsoinclude a fluid control module. The fluid control module can be coupledto the at least one inlet and can be configured to control delivery offluid to the at least one inlet. The apparatus can further include atleast one fluid source and a source of transitional fluid coupled to thefluid control module.

In embodiments, an apparatus for processing of a MEMS or semiconductordevice can include a pressure chamber having interior surfacesconstructed from a nickel-copper alloy. The pressure chamber can have atleast one fluid inlet with conduits in fluid communication with the atleast one fluid inlet. At least one of the conduits can be configured tobe coupled to a source of first fluid. At least another of the conduitscan be configured to be coupled to a source of transitional fluid.

In embodiments, an apparatus for processing of a sample can include apressure chamber, a fluid supply module, and a control system. The fluidsupply module can deliver transitional fluid and one or more otherfluids to the pressure chamber. The control system can be configured toselect and control the delivery of fluid from the fluid supply module tothe pressure chamber. The control system may also be configured to heatthe pressure chamber with transitional fluid therein to a temperatureand pressure above the critical point temperature and pressure of thetransitional fluid.

In embodiments, a method for processing a sample can include flowing afirst fluid into a sealed pressure chamber so as to contact the samplecontained within the sealed pressure chamber. The method may furtherinclude flowing a transitional fluid into the sealed pressure chamber ata first temperature and a first pressure such that the transitionalfluid in a liquid state contacts the sample. The method may also includeheating the transitional fluid in the sealed pressure chamber to asecond temperature and a second pressure. The second temperature andsecond pressure can be greater than a critical point temperature andpressure of the transitional fluid such that the transitional fluid inthe sealed pressure chamber is in a supercritical fluid state.

Objects and advantages of the present disclosure will become apparentfrom the following detailed description when considered in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments will hereinafter be described in detail below with referenceto the accompanying drawings, wherein like reference numerals representlike elements. The accompanying drawings have not necessarily been drawnto scale. Where applicable, some features may not be illustrated toassist in the description of underlying features.

FIG. 1A is a schematic diagram showing components of an integratedprocessing and drying system, according to one or more embodiments ofthe disclosed subject matter.

FIG. 1B is a schematic diagram showing components of another integratedprocessing and drying system, according to one or more embodiments ofthe disclosed subject matter.

FIG. 2 is a schematic diagram showing a configuration of fluid controlcomponents in an integrated processing and drying system, according toone or more embodiments of the disclosed subject matter.

FIG. 3 is a schematic diagram showing the configuration of a controllerfor use in an integrated processing and drying system, according to oneor more embodiments of the disclosed subject matter.

FIG. 4 is a chart showing the configuration of the various valves in anintegrated processing and drying system during various modes ofoperation, according to one or more embodiments of the disclosed subjectmatter.

FIGS. 5A-5B is a process flow diagram of a processing and drying method,according to one or more embodiments of the disclosed subject matter.

FIG. 6 is a schematic diagram showing an alternative configuration offluid control components in an integrated processing and drying system,according to one or more embodiments of the disclosed subject matter.

FIG. 7 is a schematic diagram showing another configuration of fluidcontrol components in an integrated processing and drying system,according to one or more embodiments of the disclosed subject matter.

FIG. 8 is a schematic diagram showing yet another configuration of fluidcontrol components in an integrated processing and drying system,according to one or more embodiments of the disclosed subject matter.

DETAILED DESCRIPTION

According to the disclosed embodiments, processing and drying of asample, such as a semiconductor or MEMS device, can be achieved in asingle system, in particular a single chamber. The system can include apressure chamber that holds the sample throughout the various processingsteps, such as, but not limited to, photoresist development, structurallayer etching, photoresist removal, sacrificial layer etching (i.e.,releasing), rinsing or flushing, and dehydration, as well as the dryingsteps necessary to prepare a semiconductor or MEMS device for use. Inorder to withstand the kinds of chemicals employed in the processingsteps, the pressure chamber and one or more fluid conveyances in thesystem can be formed from a chemically-resistant material. For example,the chamber and any tubing or piping leading to/from the chamber may beconstructed from a metal alloy, such as a Monel alloy. The chamber mayalso be constructed so as to handle pressure and temperature extremesthat may arise during the drying steps.

Appropriate fluid connections allow the introduction of one or moreprocessing agents, which may be in liquid or gaseous form, into thechamber to interact with the sample contained therein. For example, thechamber and associated fluid conduits may be configured to perform asacrificial layer etch followed by critical point drying (also known assupercritical drying) of a MEMS device. The fluid conduits thus allow arelease agent to be introduced into the chamber, which contains anunreleased MEMS device therein. The release agent etches and removes thesacrificial layer or layers of the MEMS device. After removal of thesacrificial layer(s), certain structures on the MEMS device are free tomove with respect to others structures on the device.

Without removing the now released MEMS device from the chamber, therelease agent in the chamber is replaced with one or more fluid washesof a flushing fluid, such as de-ionized water (DIW), followed by one ormore fluid washes of a dehydrating fluid, such as an alcohol. After thefinal alcohol wash, the MEMS device undergoes a critical point dryingprocess in the chamber using a transitional fluid, such as carbondioxide. After the completion of the drying process, the released MEMSdevice can be removed from the chamber for use or further processing.

Referring to FIG. 1A, a schematic diagram of an integrated release andcritical point drying system 100A is shown. The system 100A includes apressure chamber 102 that houses the MEMS or semiconductor devicethrough the release and drying steps. A fluid supply 106 can include avariety of fluids for the release, flush, dehydration, and dryingstages. The fluid supply 106 can include a release agent supply 124, aflushing fluid supply 126, a dehydrating fluid supply 128, and atransitional fluid supply 130. For example, the release agent supply 124can be a tank of 49% hydrofluoric (HF) acid or buffered oxide etchant(BOE). The flushing fluid supply 126 can be a tank of de-ionized (DI)water. The dehydrating fluid supply 128 can be a tank of ethanol. Thetransitional fluid supply 130 can be a pressurized tank of liquid carbondioxide.

The fluid supply 106 may additionally include one or more fluid sources(not shown) for pre- or post-processing of the MEMS or semiconductordevice. For example, a protective layer of photoresist or other materialis sometimes provided on a surface of the MEMS device to protectstructures thereon during shipment and pre-release handling of thedevice. In order to perform the sacrificial layer etch, the protectivelayer is first removed. Fluid supply 106 may include a dissolving agent,such as acetone, for removing the protective layer before beginning theother processing steps.

Gravity may provide the necessary force to convey the chemicals fromeach fluid supply 124-130 to the pressure chamber 102. Alternatively,the fluids in one or more of the fluid supplies 124-130 can bepressurized. For example, flushing fluid supply 126 may be a DI watersource that filters tap water and supplies DIW at a particular waterpressure. In another example, the transitional fluid supply 130 may be apressurized tank of carbon dioxide. The tank may hold the carbon dioxidein liquid form at a pressure of, for example, 100 psi.

Depending on the particular stage in the release and drying process, thefluid source 106 may supply the appropriate fluid to the pressurechamber 102 through inlet fluid control module 110. Inlet fluid controlmodule 110 can include, for example, manual or computer controlledvalves, check valves, pipes, tubing, pumps, flow control devices,sensors, or the like. Outlet fluid control module 112 can control thefluid flow from the pressure chamber 102, depending on the particularstage in the release and drying process. Similar to the inlet fluidcontrol module 110, outlet fluid control module 112 can include, forexample, manual or computer controlled valves, check valves, pipes,tubing, pumps, flow control devices, sensors, or the like.

Inlet fluid control module 110 and outlet fluid control module 112 mayform part of a control system 104, which controls operation of system100A during the various processing and drying steps. Control system 104can also include a controller 108, a thermal management module 114, anda pressure sensor 122. Controller 108 is operatively coupled to thevarious components of the control system 104 for automatic control ofthe operation of system 100A in executing the various processing anddrying steps on the sample contained in chamber 102.

Thermal management module 114 includes a temperature sensor 116 whichmonitors a temperature of the interior volume of the pressure chamber.Monitoring of the temperature of the pressure chamber 102 may beespecially important during the critical point drying process. Cooler120 is thermally coupled to the pressure chamber 102. For example,cooler 120 may be a thermoelectric cooler, refrigeration loop, or othercooling devices, as known in the art. Controller 108 controls cooler 120in response to temperature readings from temperature sensor 116 to coolthe interior volume of the pressure chamber to a temperature at whichtransitional fluid introduced into the pressure chamber is in a liquidstate. When the transitional fluid is carbon dioxide, this temperaturemay be, for example, less than 10° C.

Heater 118 is also thermally coupled to the pressure chamber 118. Forexample, heater 118 may be a thermoelectric heater, resistive heater, orother heating devices, as known in the art. Controller 108 controlsheater 118 in response to temperature readings from temperature sensor118 and to heat the interior volume of the pressure chamber to atemperature and pressure greater than the critical point temperature andpressure of the transitional fluid. Controller 108 may optionally alsomonitor pressure readings from pressure sensor 122 during the heatingprocess. Above the critical point temperature and pressure, thetransitional fluid contained in the pressure chamber transitions to asupercritical fluid state. When the transitional fluid is carbondioxide, the critical point temperature and pressure is 31° C. and 1072psi, respectively.

Although the discussion above focuses on a release and drying system forMEMS or semiconductor devices, the teachings herein have application toa wide variety of samples and processes. Additional fluid supplies maybe added to fluid supply 106 to enable a variety of processingtechniques to be performed on a sample without moving the sample fromthe pressure chamber. Alternatively, the system 100A may be constructedsuch that the sample can be disposed in the pressure chamber for a firstseries of process steps, removed from the chamber for a second series ofprocess steps, and then returned to the chamber for a final series ofprocess steps and/or drying steps.

Referring to FIG. 1B, a system 100B is shown which includes additionalfluid supplies for performing different process steps as compared withsystem 100A of FIG. 1A. Fluid supply 106B thus includes a first fluidsupply 132B, a second fluid supply 134B, a third fluid supply 136B, afourth fluid supply 124B, a fifth fluid supply 126B, a sixth fluidsupply 128B, and a transitional fluid supply 130. Each of the fluidsupplies in fluid supply 106B is coupled to the inlet fluid controlmodule 110B for controlling fluid flow to the pressure chamber 102. Theadditional fluid supplies 132B, 134B, and 136B, as compared with system100A of FIG. 1A, allow for additional processing steps to be performedprior to release and critical point drying steps. The number of fluidsources shown in FIG. 1B is for illustrative purposes only. Additionalor fewer fluid sources in fluid supply 106B or separate from fluidsupply 106B are also possible according to one or more contemplatedembodiments.

For example, the sample introduced into the pressure chamber 102 may bea semiconductor device that has undergone a photolithographic process.The device may have exposed but not yet developed patterns in aphotoresist layer on a surface of the device. The first fluid supply132B may thus be a photoresist developer. The pattern in the photoresistmay be developed (i.e., portions of the photoresist removed) byintroducing the photoresist developer into the sealed pressure chamberwith the semiconductor device therein. The second fluid supply 134B maybe a structural layer etchant, such as potassium hydroxide (KOH). Oncethe pattern is formed in the photoresist layer, fluid from the secondfluid supply 134B may be introduced into the pressure chamber to etch aportion of the semiconductor device using the patterned photoresistlayer as a mask. The third fluid supply 136B may be a substance forremoval of photoresist, such as acetone. The third fluid can beintroduced after the etching of the semiconductor device and flushing ofthe pressure chamber is complete. Between each of the above processingsteps, the chamber 102 may be flushed with a rinsing agent, such as DIWcontained in fifth fluid supply 126B. Similar to the configuration ofsystem 100A, fourth fluid supply 124B (e.g., sacrificial layer etchant),fifth fluid supply 126B (e.g., flushing fluid), and sixth fluid supply128B (e.g., dehydrating fluid) can be introduced sequentially into thepressure chamber to release structures of the semiconductor device andprepare it for critical point drying.

Of course, the fluids in the various fluid supplies of fluid supply 106Bare not limited to those disclosed above, nor are the potentialprocesses limited to etching or developing. Rather, the construction andconfiguration of the pressure chamber and associated fluid conveyancesand controls allow the integration of various manufacturing processsteps, including critical point drying, into a single setup. Thepressure chamber may thus include various components, such as agitatorsor stirring rods, which may be applicable to one or more of theprocesses. Whereas prior techniques required separate stations ordevices for processing of a sample, the integrated processing and dryingsystems of the present disclosure thus a sample to undergo multipleprocesses and drying in a single station without removal of the samplefrom the pressure chamber.

Referring now to FIG. 2, a setup for the inlet fluid control module 110and the outlet fluid control module 112 within system 100 is shown.Inlet fluid control module 110 can include components of the primaryinlet line 232 as well as components for conveying fluid from the fluidsources 124-130 to the inlet line 232. The primary inlet line 232 isconnected to an inlet 216 of pressure chamber 102. Primary inlet line232 can be constructed from one or more pipe or tube segments and caninclude one or more fluid control components within the flow path. Forexample, a controllable main line valve 212 is provided in flow path 232to control the flow of fluid flowing therethrough and into pressurechamber 102 through inlet 216. A check valve 214 may also be provided inflow path 232 to prevent backflow in the primary inlet line 232, i.e.,flow of fluid from pressure chamber 102 back into primary inlet line232.

A fluid input column 210 can connect each of the fluid supplies 124-130to the primary inlet line 232 through individual input lines. Forexample, release agent supply 124 can be connected to the fluid inputcolumn 210 by a first input line 230. First input line 230 can alsoinclude a controllable release agent valve 202 to control the flow ofrelease agent from the supply 124 to the fluid input column 210 andthereby to primary inlet line 232. Flushing fluid supply 126 can beconnected to the fluid input column 210 by a second input line 238.Second input line 238 can include a controllable flushing fluid valve204 to control the flow of flushing fluid from the supply 126 to thefluid input column 210 and thereby to the primary inlet line 232.Dehydrating fluid supply 128 can be connected to the fluid input column210 by a third input line 240. Third input line 240 can include acontrollable dehydrating fluid valve 204 to control the flow ofdehydrating fluid from the supply 128 to the fluid input column 210 andthereby to the primary inlet line 232. Transitional fluid supply 130 canbe connected to the fluid input column 210 by a fourth input line 242.Fourth input line 242 can include a controllable transitional fluidvalve 208 to control the flow of transitional fluid from the supply 130to the fluid input column 210 and thereby to the primary inlet line 232.

The outlet fluid control module 112 can include components of a mainvent line 234 and a secondary bleed line 236. The main vent line 234 isconnected to a primary outlet 224 of pressure chamber 102. Main ventline 234 can be constructed from one or more pipe or tube segments andcan include one or more fluid control components within the flow path.For example, a controllable purge valve 226 is provided in flow path 234to control the flow of fluid from the outlet 224 of the pressure chamber102. A check valve 228 may also be provided in flow path 234 to preventany backflow of exhausted fluid into the pressure chamber 102.

Secondary bleed line 236 is connected to a secondary outlet 218 ofpressure chamber 102. Secondary bleed line can be constructed from oneor more pipe or tube segments and can include one or more fluid controlcomponents within the flow path. For example, a controllable bleed valve220 is provided in flow path 236 to control the flow of fluid fromsecondary outlet 218 of the pressure chamber 102. A check valve 222 mayalso be provided in flow path 236 to prevent any backflow of exhaustedfluid into the pressure chamber 102.

Note that the output of the main vent line 234 may be discarded as wasteor recycled for re-use in the integrated system 100 or other systems, asappropriate. Likewise the output of the secondary bleed line 236 may bediscarded as waste or recycled for re-use. Alternatively, when theoutput of the secondary bleed line 236 is a naturally occurring gas(e.g., carbon dioxide), the output may be exhausted to the atmosphere.

Various other fluid flow control configurations besides thoseillustrated in FIG. 2 are also possible. For example, the relativeposition of controllable valves and check valves in a particular flowpath may be reversed. It is further emphasized that the figures hereinhave not been drawn to scale, nor does the relative position ofcomponents illustrated in the figures necessarily represent actual orintended positions of the components in practical embodiments. Forexample, although valve 226 has been illustrated in FIG. 2 as beingpositioned at a particular distance from pressure chamber 102, in anactual device the distance between outlet 224 and valve 226 may beminimized or omitted. Accordingly, embodiments of the disclosed subjectmatter are not intended to be limited to the particular spatialarrangements and configurations illustrated in the figures.

Because of the caustic chemicals employed in various processing steps,the chamber 102, as well as fluid flow components in the inlet andoutlet fluid control modules 110 and 112, can be made from a materialthat can withstand exposure to these chemicals as well as thetemperature and pressure extremes of the drying process. For example,the chamber 102, inlet fluid control module 110, and outlet fluidcontrol module 112 can be made from a Monel alloy. Monel is anickel-copper alloy containing about 60% nickel, about 38% copper, andsmall amounts of iron, manganese, carbon, silicon, or other elements.For example, Monel Alloy 400 can include at least 63% nickel, at most2.5% iron, at most 2% manganese, at most 0.5% silicon, between 28% and34% copper, at most 0.3% carbon, and at most 0.024% sulfur. Monel AlloyK-500 can include 66.5% nickel, 2.0% iron, 1.5% manganese, 0.5% silicon,2.7% aluminum, 0.5% titanium, 30% copper, and 0.01% sulfur.

Various other types of metals and/or metal alloys may also be employedfor the pressure chamber and fluid control modules depending on the typeof chemicals in the processing and drying steps and the chemicalresistance of the metal or alloy thereto. Such metals and metals alloysmay include, but are not limited to, nickel, nickel alloys,nickel-iron-chromium alloys, nickel-chromium alloys, nickel-copperalloys, and stainless steel. When the processing steps employ a releaseagent such as hydrofluoric acid, the pressure chamber and fluid controlmodules are preferably constructed from a nickel-copper alloy such as aMonel alloy, which demonstrates sufficient chemical resistance tohydrofluoric acid.

As the use of Monel alloy is designed to protect components from causticchemicals and withstand pressures of the drying process, Monel alloy maybe used for any of the fluid conveyance components that will be exposedto both the caustic chemicals of the processing steps and elevatedpressures of the drying steps. Those components that are exposed tocaustic chemicals but not drying step pressures may be constructed froma Monel alloy or another chemically resistant material, such aspolytetrafluoroethylene (PTFE). Those components of the integratedsystem that are not exposed to any caustic chemicals but are exposed todrying step pressures may be constructed from a Monel alloy or othermaterial sufficiently strong to withstand said pressures, such as steel.Those components of the integrated system that are not exposed to anycaustic chemicals or drying step pressures may be constructed from aMonel alloy or any other material capable of containing the conveyedfluid.

Referring again to FIG. 2, release agent supply 124 would normallycontain the caustic chemicals while the remaining fluid supplies 126-130would normally be considered non-caustic. Thus, valve 202 and releaseagent input line 230 may be constructed from a Monel alloy or achemically resistant polymer. Valves 204-208 and input lines 238-242 maybe constructed from Monel alloy, steel or other metal, or a polymer.Fluid input column 210 would also be exposed to caustic chemicals duringthe release process, but would not normally be exposed to releaseprocess pressures due to check valve 214. Thus, fluid input column 210may be constructed from a Monel alloy or a chemically resistant polymer.Valve 212, check valve 214, components of input line 232, and pressurechamber 102 would be exposed to caustic chemicals during the releaseprocess and may be exposed to drying process pressures as well. The samewould be true of the components of output fluid control module 112.Accordingly, valve 212, check valve 214, input line 232, pressurechamber 102, and the components of output fluid control module 112 mayall be constructed from Monel alloy.

Referring now to FIGS. 2 and 3, controller 108 can include one or moreprocessors 302 operatively coupled with one or more memories 304. Thememory 304 or other computer-readable medium can include instructionsthereon capable of executing the various steps or stages of theintegrated processing and drying methods described herein. The processor302 may be operatively connected to the various controllable valves inthe inlet fluid control module and outlet fluid control module tocontrol fluid flow through the system 100. The processor 302 can also beconnected to one or more sensors for monitoring the condition of thesystem 100. For example, temperature sensor 116 and pressure sensor 122can send information regarding the temperature and pressure,respectively, to the controller 108 for use in controlling heater 118 orcooler 120.

Controller 108 may also send control signals to one or more valves tocause the valves to fully open, partially open, or close. For example,controller 108 may control first fluid (e.g., release agent) valve 202,second fluid (e.g., flushing fluid) valve 204, third fluid (e.g.,dehydrating agent) valve 206, transitional fluid valve 208, main linevalve 212, bleed valve 220, and/or purge valve 226. One or more flowsensors, such as inlet flow sensor 308 and outlet flow sensor 310, maycommunicate the status of fluid flow within the system 100 to controller108 to control operation of the valves responsively thereto. A chamberseal sensor 316 may also be provided so that the controller 108 does notproceed with the processing and drying steps unless the chamber sealsensor 316 indicates that the pressure chamber 102 has beenappropriately closed and sealed.

Referring now to FIGS. 4-5, a process that can be executed by anintegrated system 100A/100B in processing a sample, for example a MEMSdevice, is described. FIG. 4 is a chart showing the various valve statesduring different stages in a release and drying method for a MEMSdevice, while FIG. 5 is a flow chart showing steps in a generalizedprocessing and drying method.

The method begins at 502 with processing stage 500A, shown in FIG. 5A,before proceeding to a drying stage 500B, shown in FIG. 5B. The methodproceeds to step 504 where the sample, such as an unreleased MEMSdevice, is placed in pressure chamber 102. At this point, all valves inthe system are closed, as no fluid flow is necessary. In step 506, thepressure chamber 108 is manually or automatically sealed with the samplecontained therein. The method proceeds to step 508 where a countervariable, n, corresponding to the particular fluid for introduction intothe pressure chamber is set to 1. For example, the first fluid to beintroduced into the chamber can be a sacrificial layer etchant. Themethod then proceeds to step 510.

In step 510, the controller 108 commands the n^(th) fluid valve and themain line valve 212 to open while all other valves remain closed suchthat the pressure chamber 102 is filled with the n^(th) fluid. Forexample, when the first fluid is a release agent, release agent valve202 may be opened while all other valves remain closed so as to fill thepressure chamber 102 with the release agent. Once the chamber is filled,the valves may be closed. The n^(th) fluid may be maintained in thepressure chamber 102 for a predetermined period of time. For example,when the first fluid is a release agent, the first fluid may bemaintained in the pressure chamber for a sufficient period of time tocompletely etch the sacrificial layers of the MEMS device, therebyresulting in the release of said device. The method may then proceed tostep 516.

Alternatively, the n^(th) fluid in the pressure chamber 102 may bereplaced with one or more exchanges of fresh n^(th) fluid. In such analternative, the method proceeds to step 512 where it is determined ifthe n^(th) fluid introduction should be repeated with fresh fluid. Ifso, the method proceeds to step 514. For example, when the first fluidis a release agent and is to be replaced with fresh release agent, thecontroller 108 can command the release agent valve 202, the main linevalve 212, and the purge valve 226 to open while all other valves remainclosed. After a sufficient time to allow the volume in the pressurechamber 102 to be exchanged with fresh n^(th) fluid, the method thenproceeds back to step 512. After step 512, if no further exchanges areneeded, the method proceeds to step 516.

In still another alternative, fresh n^(th) fluid may be continuouslyflowed through the pressure chamber 102 while removing fluid from thepressure chamber 102 rather than having separate fill, dwell, andexchange steps. After a sufficient time of continuous flow, the methodproceeds to step 516.

In step 516, the counter variable, n, is compared with the total numberof fluid sources,

N, to be introduced into the pressure chamber. If n is less than N, thenthe method proceeds to step 518. Steps 514, 510, 512, and 516 can thenbe repeated until all fluids have been sequentially introduced into thepressure chamber (i.e., until n=N).

For example, in a release process, the total number of fluids may bethree (i.e., N=3) with the first fluid (n=1) being the release agent.The second fluid (n=2) may be a flushing fluid, such as DIW. Thus, instep 514 for the iteration with n=2, the release agent in the pressurechamber 102 is replaced with flushing fluid. First, the pressure chamber102 is purged to remove the release agent. Controller 108 commandsflushing fluid valve 204, main line valve 212, and purge valve 226 toopen while all other valves remain closed such that flushing fluid fillsthe pressure chamber 102 as the contents of the pressure chamber 102 areremoved via the main vent line 234. After a predetermined time (or,alternatively, after a predetermined volume of flushing fluid has flowedthrough the pressure chamber), the pressure chamber 102 may be filledwith flushing fluid by closing purge valve 226. After the fill withflushing fluid in step 510, the method may dwell for a predeterminedperiod of time to allow the flushing fluid to fully penetrate thereleased MEMS or semiconductor device. The method then proceeds to step516.

Alternatively, the flushing fluid in the pressure chamber 102 may bereplaced with one or more exchanges of fresh flushing fluid. In such analternative, the process proceeds to step 512 where it is determined ifthe flushing fluid should be repeated with a fresh bath. For example,the flushing fluid fill may be repeated two additional times for a totalof three flushing fluid baths. If so, the process proceeds to step 514.The controller 108 can command the flushing fluid valve 204, the mainline valve 212, and the purge valve 226 to open while all other valvesremain closed. After a sufficient time to allow the volume in thepressure chamber 102 to be exchanged with fresh flushing fluid, theprocess then proceeds back to the fill and dwell portions of step 510.After step 510, if no further exchanges are needed, the process proceedsto step 516.

In still another alternative, fresh flushing fluid may be continuouslyflowed through the pressure chamber 102 while removing fluid from thepressure chamber 102 rather than having separate fill, dwell, andexchange steps. After a sufficient time of continuous flow, the processproceeds to step 516.

The third fluid (n=3) may be a dehydrating fluid, such as ethanol orisopropyl alcohol (IPA). Thus, in step 514 for the iteration with n=3,the flushing fluid in the pressure chamber 102 is replaced withdehydrating fluid. First, the pressure chamber 102 is purged to removethe flushing fluid. Controller 108 commands dehydrating fluid valve 206,main line valve 212, and purge valve 226 to open while all other valvesremain closed such that dehydrating fluid fills the pressure chamber 102as the contents of the pressure chamber 102 are removed via the mainvent line 234. After a predetermined time (or, alternatively, after apredetermined volume of dehydrating fluid has flowed through thepressure chamber), the pressure chamber 102 may be filled withdehydrating fluid by closing purge valve 226. After the fill withdehydrating fluid, the method may dwell for a predetermined period oftime to allow the dehydrating fluid to fully penetrate the released MEMSor semiconductor device. The method can then proceed to step 516.

Alternatively, the dehydrating fluid in the pressure chamber 102 may bereplaced with one or more exchanges of fresh dehydrating fluid. In suchan alternative, the method proceeds to step 512 where it is determinedif the dehydrating fluid should be repeated with a fresh bath. Forexample, the dehydrating fluid fill may be repeated two additional timesfor a total of three dehydrating fluid baths. If so, the method proceedsto step 514. The controller 108 can command the dehydrating fluid valve206, the main line valve 212, and the purge valve 226 to open while allother valves remain closed. After a sufficient time to allow the volumein the pressure chamber 102 to be exchanged with fresh dehydratingfluid, the method then proceeds back to the fill and dwell portions ofstep 510. After step 510, if no further exchanges are needed, the methodcan proceed to step 516.

In still another alternative, fresh dehydrating fluid may becontinuously flowed through the pressure chamber 102 while removingfluid from the pressure chamber 102 rather than having separate fill,dwell, and exchange steps. After a sufficient time of continuous flow,the method can proceed to step 516.

Once all of the desired processing fluids have been introduced into thepressure chamber, the method proceeds from step 516 to the first step ofthe drying process 500B. Referring to FIG. 5B, the method continues withthe first step 526 in the drying stage 500B. In step 526, the chamber iscooled to a temperature sufficient for introduction of the transitionalfluid into the pressure chamber 102 in a liquid phase. For example, whenthe transitional fluid is carbon dioxide, the pressure chamber 102 maybe cooled to a temperature less than or equal to 10° C. The controller108 may control cooler 120 to achieve the desired cooling. At thispoint, all valves in the system may be closed since fluid flow may notbe necessary. After achieving the temperature, the method proceeds tostep 528; however, the controller 108 may command the cooler 120 toprovide additional cooling during steps 528-532 so as to maintain thetemperature of the pressure chamber below the desired liquid phasetemperature.

In step 528, the fluid in the pressure chamber 102 is replaced withliquid transitional fluid. For example, the transitional fluid may becarbon dioxide. First, the pressure chamber 102 is purged to remove thefluid therein (e.g., dehydrating fluid). Controller 108 commandstransitional fluid valve 208, main line valve 212, and purge valve 226to open while all other valves remain closed such that transitionalfluid fills the pressure chamber 102 as the contents of the pressurechamber 102 are removed via the main vent line 234. After apredetermined time (or, alternatively, after a predetermined volume oftransitional fluid has flowed through the pressure chamber), thepressure chamber 102 may be filled with transitional fluid by closingpurge valve 226. After the fill with transitional fluid, the process maydwell for a predetermined period of time to allow the liquidtransitional fluid to fully penetrate the sample. The method thenproceeds to step 534.

Alternatively, the transitional fluid in the pressure chamber 102 may bereplaced with one or more exchanges of fresh transitional fluid. In suchan alternative, the method proceeds to step 530 where it is determinedif the transitional fluid should be repeated with fresh fluid. Forexample, the transitional fluid fill may be repeated two additionaltimes for a total of three transitional fluid baths. If so, the processproceeds to step 532. The controller 108 can command the transitionalfluid valve 208, the main line valve 212, and the purge valve 226 toopen while all other valves remain closed. After a sufficient time toallow the volume in the pressure chamber 102 to be exchanged with freshtransitional fluid, the method then proceeds back to the fill and dwellportions of step 528. After step 528, if no further exchanges areneeded, the method proceeds to step 534.

In still another alternative, fresh transitional fluid may becontinuously flowed through the pressure chamber 102 while removingfluid from the pressure chamber 102 rather than having separate fill,dwell, and exchange steps. After a sufficient time of continuous flow,the method proceeds to step 534.

In step 534, the pressure chamber 102 is heated to achieve a temperatureand pressure exceeding the critical point of the transitional fluid,such that the transitional fluid is contained in the pressure chamber ina supercritical fluid state. For example, when carbon dioxide is used asthe transitional fluid, the pressure chamber is heated to a temperatureand pressure in excess of the critical point of 31° C. and 1072 psi. Thecontroller 108 may control heater 118 to achieve the desired heating. Atthis point, all valves in the system may be closed since fluid flow maynot be necessary. After achieving the temperature, the method proceedsto step 536; however, the controller 108 may command the heater 118 toprovide additional heating during step 536 so as to maintain thetemperature of the pressure chamber above the desired critical pointtemperature. The method then proceeds to step 536.

In step 536, the transitional fluid is exhausted from the pressurechamber 102. First, the pressure in the chamber is slowly reduced by“bleeding” the transitional fluid from the pressure chamber 102 via thesecondary bleed line. The controller 108 may command all of the valvesin the system to close except for bleed valve 220. Bleed valve 220 maybe calibrated to maintain a specified low flow rate such that thepressure in the chamber decreases at a predetermined rate. For example,the bleed valve may be calibrated such that the flow rate oftransitional fluid through the secondary bleed line results in a rate ofpressure drop in the pressure chamber 102 between 100 psi/minute and 150psi/minute. Alternatively, controller 108 can monitor the flow ratethrough the secondary bleed line via outlet flow sensor 310 and/or thepressure in the chamber via sensor 122 and adjust bleed valve 220 toachieve the desired rate of pressure drop.

Once the pressure in the chamber 102 reaches a sufficiently lowpressure, the controller 108 may then vent the chamber 102. For example,the chamber 108 may begin venting the chamber 102 once the pressure inthe chamber is less than or equal to 400 psi. The controller may commandall of the valves in the system to close except for purge valve 226 suchthat transitional fluid in the pressure chamber 102 is exhausted throughmain vent line 234. Purge valve 226 may allow for much faster exhaustthan the bleed valve 220 would allow. Once the pressure in the chamberis equal to atmospheric pressure, the method can then proceed to step538. In step 538, the sample has finished undergoing the variousprocessing and drying steps. The pressure chamber 102 can be unsealed,and the sample can be removed for subsequent processing and/or use. Themethod thus terminates at 540.

Although automated control using controller 108 is described above, theteachings of the present disclosure are equally applicable to manual orsemi-automated systems as well. In particular, controller 108 may bereplaced by manual input from a user, such as by manually actuatingvalves of inlet fluid control module 110 and outlet fluid control module112. Moreover, controller 108 can execute the various processing anddrying steps on a semi-automated basis, such as in response to commandsor input from the user through a user interface. In addition, controller108 can be configured to operate in a normally automatic mode to executethe processing and drying steps without user input and to operate on asemi-automatic basis based on user input through a user interface.Furthermore, the controller 108 can be configured to allow customizationof the processing and/or drying steps by a user. For example, a user canprogram the controller 108 to adjust the amount of time of a particularprocessing or drying step, the flow configurations of a particularprocessing or drying step, the order of processing or drying steps, oreven which steps should or should not be performed.

The controller 108 can also be configured to perform one or more of theprocessing or drying steps without performing others of the processingor drying steps. For example, if stiction is not an issue with aparticular device design, a user may program the controller 108 toexecute just a sacrificial layer etch and DIW flush. In another example,if the device has already been released and dehydrated, the controller108 may be programmed to perform only the drying steps.

In other configurations, one or more functions of the controller may bereplaced with manual or mechanical control. For example, an operator maycontrol operation of the valves and/or thermal management module inresponse to time or temperature cues. Accordingly, the controller may bepartially or completely omitted. In other configurations, mechanical orelectrical timers may be used in lieu of a computer or processor tocontrol operation of system 100A/100B, valves of the fluid controlmodules 110 and 112, and thermal management module 114. Moreover, thecontroller 108 can be integrated with other controller components, forexample, in a MEMS or semiconductor device manufacturing assemblyprocess. Thus, one or more controllers or a central controller for theMEMS or semiconductor device assembly line may control operation of theintegrated release and drying system 100.

The use of Monel alloy, or other chemically and pressure resistantmaterials, for the pressure chamber and fluid conduits allows a singlesystem to be used for both processing and drying steps without having tomove the sample between different processing machines or apparatuses.However, Monel alloy may be relatively difficult to machine as comparedto other metals, such as steel, and can lead to significant increases inmanufacturing and materials costs. As such, it may be advantageous tominimize the use of Monel alloy, especially for those portions that maynot see caustic chemicals during normal operation. Accordingly, thepressure chamber may be configured such that at least the interiorsurfaces thereof and the fluid passages therethrough are formed of aMonel alloy or similar chemically-resistant material.

Referring now to FIG. 6, an alternative configuration for inlet andoutlet fluid control modules of an integrated system 600 for release anddrying is shown. System 600 is substantially similar to theconfiguration of system 100 illustrated in FIG. 2 with the exception ofthe configuration of the inlet fluid control module. In particular,fluid input column 610 connects each of the fluid sources 126-130 to asecondary inlet line 608 via the individual input lines. A check valve612 in secondary inlet line 608 can prevent backflow from primary inletline 604 into the fluid column 610. Release agent supply 124 isseparately connected to a primary inlet line 604 through first inputline 230. A T-connector 606 joins the first input line 230 to theprimary inlet line 604, and the secondary inlet line 608. Because anycontact with the caustic agent in the inlet fluid control module isisolated to the first input line 230, the primary inlet line 604, andthe lower portion of the secondary inlet line 608, the use of Monelalloy or other chemically resistant material can be confined to theseareas, thereby minimizing the use of these materials. Of course, thepressure chamber 102 and components of the outlet fluid control modulewill still need to be constructed from a Monel alloy or other chemicallyresistant material as their contact with the caustic agent has not beenaltered.

Referring now to FIG. 7, yet another alternative configuration for inletand outlet fluid control modules of an integrated system 700 for releaseand drying is shown. System 700 is substantially similar to theconfiguration of system 600 illustrated in FIG. 6 with the exception ofthe configuration of the pressure chamber and the inlet fluid controlmodule with respect to the non-caustic fluid sources. In particular,fluid input column 610 connects each of the fluid sources 126-130 to asecondary inlet line 702 via the individual input lines. The secondaryinlet line 702 is directly connected to a secondary inlet 216 b ofpressure chamber 102′. Release agent supply 124 is separately connectedto the primary inlet 216 b of the pressure chamber 102′ via first inputline 230. Because any contact with the caustic agent in the inlet fluidcontrol module is isolated to the first input line 230, the use of Monelalloy or other chemically resistant material can be confined to thefirst input line 230, thereby minimizing the use of these materials. Ofcourse, the pressure chamber 102′ and components of the outlet fluidcontrol module will still need to be constructed from a Monel alloy orother chemically resistant material as their contact with the causticagent has not been altered.

As discussed above, various passive mechanisms (e.g., gravity, tankpressure) may be employed to provide fluid flow out of the respectivefluid sources into the inlet fluid control module and pressure chamber.Active fluid conveyance mechanisms may also be used. For example, one ormore pumps may be employed in the inlet fluid control module and/or theoutlet fluid control module. Alternatively, one or more pumps may beemployed in the fluid supply 106 itself. Other types of fluid conveyancemechanisms may also be employed.

Referring now to FIG. 8, a configuration for inlet and outlet fluidcontrol modules of an integrated system 800 employing a pump is shown.System 800 is substantially similar to the configuration of system 100illustrated in FIG. 2 but with the addition of a pump 802 in the inletfluid control module. In particular, pump 802 has replaced valve 212 ininlet line 232. As the pump may be exposed to the caustic chemicalsemployed in the release process, at least the surfaces of the pump incontact with the chemicals can be constructed of a chemically resistantmaterial. Alternatively, the pump can be constructed so as to avoidcontact with the fluid. For example, the pump may be a peristaltic pumpif the tubing in inlet line 232 is sufficiently flexible to allowcompression by the rollers of the peristaltic pump without permanentdeformation. Of course, one or more pumps may be provided elsewherewithin the integrated release and drying system as needed.

The embodiments of FIGS. 2 and 6-8 have been discussed with respect tothe configuration of FIG. 1A; however, the embodiments of FIGS. 2, and6-8 are equally applicable to the configuration of FIG. 1B withappropriate modifications to accommodate the additional fluid supplies.

The integrated processing and drying systems described herein may beintegrated into a MEMS or semiconductor device assembly line so as toform a portion of an overall manufacturing system. Alternatively, theintegrated processing and drying systems may be embodied as a separateunit, either at a same location as the overall MEMS or semiconductordevice assembly line or remote therefrom. For example, the integratedprocessing and drying system 100 may be disposed at the location of anintermediate manufacturer or an end user of the MEMS or semiconductordevice. The MEMS or semiconductor devices may be shipped from theprimary manufacturer to the intermediate manufacturer or end userwithout releasing so as to prevent damage to the individual structuresthereon.

While specific configurations have been illustrated in the accompanyingfigures and discussed in detail herein, configurations and embodimentsaccording to the present disclosure are not limited thereto. Moreover,although specific chemicals have been discussed, other chemicals may beused as well. For example, other etchants besides 49% HF may be used.Such etchants may include, but are not limited to, buffered oxideetchant (BOE), potassium hydroxide (KOH), or gold etchant. In stillanother example, other transitional fluids, such as, but not limited to,hydrogen, oxygen, nitrogen, and carbon monoxide, can be used accordingto contemplated embodiments of the disclosed subject matter. Inaddition, the systems, methods, and devices described herein can beapplied to non-semiconductor and non-MEMS devices as well. For example,the techniques described herein may be applied to the processing anddrying of gels or biological material.

Moreover, the recitation of fluid herein is not intended to be limitedto substances in a liquid state. Rather, substances in a gaseous orsupercritical fluid state are also encompassed by the use of the termfluid. Thus, fluids introduced into the pressure chamber need not be aliquid to be considered a fluid. For example, the fluid may be a gaseousetchant, such as xenon difluoride (XeF₂) for etching of silicon. Allchemicals and compositions described herein are for illustrationpurposes only and should not be understood as limiting of theembodiments of the disclosed subject matter. Furthermore, the foregoingdescriptions apply, in some cases, to examples generated in alaboratory, but these examples can be extended to production techniques.Where quantities and techniques apply to the laboratory examples, theyshould not be understood as limiting.

It is, thus, apparent that there is provided, in accordance with thepresent disclosure, integrated processing and drying systems, methods,and devices for semiconductor and/or MEMS devices. Many alternatives,modifications, and variations are enabled by the present disclosure.Features of the disclosed embodiments can be combined, rearranged,omitted, etc., within the scope of the invention to produce additionalembodiments. Furthermore, certain features may sometimes be used toadvantage without a corresponding use of other features. Accordingly,Applicant intends to embrace all such alternatives, modifications,equivalents, and variations that are within the spirit and scope of thepresent invention.

1. A method for processing a sample, the method comprising: (a) sealing the sample in an interior volume of a pressure chamber, surfaces of the pressure chamber that define the interior volume being formed of a nickel-copper alloy; (b) flowing hydrofluoric acid into the sealed pressure chamber so as to fill the interior volume with the hydrofluoric acid, the hydrofluoric acid being in contact with the sample; (c) removing the hydrofluoric acid from the sealed pressure chamber; (d) after (c), cooling the interior volume of the pressure chamber to a temperature less than 10° C.; (e) flowing liquid carbon dioxide into the sealed pressure chamber so as to fill the interior volume with the liquid carbon dioxide, the liquid carbon dioxide being in contact with the sample; (f) after (e), heating the interior volume of the pressure chamber to a temperature greater than 31° C. and a pressure greater than 1072 psi; (g) after (f), exhausting gaseous carbon dioxide from the sealed pressure chamber until the pressure therein is substantially equal to atmospheric pressure.
 2. The method of claim 1, wherein the sample is a MEMS device or a semiconductor device.
 3. The method of claim 2, wherein the hydrofluoric acid is 49% HF.
 4. The method of claim 2, wherein the hydrofluoric acid is effective to etch a sacrificial layer of said MEMS or semiconductor device.
 5. The method of claim 1, wherein (c) removing the hydrofluoric acid includes: (c1) flowing water into the interior volume of the sealed pressure chamber while exhausting fluid therefrom so as to fill the interior volume with the water.
 6. The method of claim 5, further comprising, after (c1) flowing water but before (d) cooling the interior volume, flowing alcohol into the interior volume of the sealed pressure chamber while exhausting fluid therefrom so as to fill the interior volume with the alcohol.
 7. The method of claim 6, wherein the alcohol is one of ethanol, isopropanol, and methanol.
 8. The method of claim 6, wherein (e) flowing liquid carbon dioxide is such that the alcohol in the interior volume is replaced by the liquid carbon dioxide.
 9. The method of claim 1, wherein the nickel-copper alloy has about 60% nickel and about 30% copper.
 10. An apparatus for processing a sample, the apparatus comprising: a pressure chamber having an interior volume constructed to receive the sample therein, surfaces of the pressure chamber that define said interior volume being formed of a nickel-copper alloy, the pressure chamber having at least one inlet for introducing fluids into the interior volume; a first conduit in fluid communication with the at least one inlet, the first conduit being configured to be coupled to a source of hydrofluoric acid and being formed of a nickel-copper alloy; and a second conduit in fluid communication with the at least one inlet, the second conduit being configured to be coupled to a source of carbon dioxide.
 11. The apparatus of claim 10, wherein the nickel-copper alloy has about 60% nickel and about 30% copper.
 12. The apparatus of claim 10, further comprising: a valve located upstream of the at least one inlet for controlling fluid flow thereto, wherein at least a portion of the valve is formed of a nickel-copper alloy.
 13. The apparatus of claim 10, further comprising: a third conduit in fluid communication with the at least one inlet, the third conduit being configured to be coupled to a source of water; and a fourth conduit in fluid communication with the at least one inlet, the fourth conduit being configured to be coupled to a source of alcohol. 